Short case tips - Third nerve palsy

 


This patient has complete ptosis of the right eye.

When the eye lid is pulled up, it's seen that the eye is deviated outward and downward.


Those two findings indicate that this is a third nerve palsy.


Pupils of both eyes are equal.

Pupil involvement (Fixed dilated pupil) is seen if the third nerve is compressed, because the parasympathetic fibers travel on the surface of the nerve.

Conversely in non-compressive (Medical) third nerve palsies the pupil is spared.


So this patient has right medical third nerve palsy.


Lesions in various places can give rise to different presentations. For example..

    Brain stem - The 6th nerve and other long tracts are close-by. So they will have involvement of either of those.

    Cavernous sinus - A lot of structures pass adjacent to the nerve. So they will be involved.


Now since none of those are affected, the lesion is probably in the nerve itself. 

Common causes are diabetes and hypertension.

Any other condition which causes mono-neuritis can also cause a similar presentation. Eg: Vasculitis


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